Dielectric exploration and PD detection in high voltage insulation

Polymeric materials degrade over time, leading to insulation failures. Finding new materials with strong dielectric properties and robust mechanical strength is crucial for reliable electricity supply. These materials must address defects from manufacturing faults, water tree traces, or mechanical stresses. Polyurethane (PU) is known for its self-healing properties, notably its ability to recover from surface dents due to high elasticity. However, self-healing decreases with increased hardness. This study investigates PU's dielectric breakdown properties at varying hardness levels, revealing an increase in breakdown strength with hardness. Balancing hardness and self-healing are essential, providing insights into PU's dielectric properties. In parallel to engineering novel insulating materials, detecting defects early is crucial to prevent deterioration from partial discharges (PDs). Detecting PDs using acoustic emission (AE) signals is not fully explored for cable insulation. Therefore, the study investigates acoustic pulse propagation from PD events in polymer using finite element methods (FEM) in COMSOL. An analytical model in MATLAB quantifies the impact of multiple propagation paths in a cylinder, aided by a Perfect Matched Layer (PML) in the COMSOL model for reflection-free modelling. The models reveal that acoustic pulse magnitudes decrease rapidly with distance, following the inverse square law. Moreover, the study also explores the effects of PU hardness on the propagation characteristics of the AE signal, revealing a high decay rate in AE signal peak magnitude and energy with increasing PU hardness. Frequency spectra analysis indicates stronger attenuation of higher frequency components with distance. The study's revelations on the impact of PU hardness on AE signal characteristics provide engineers with valuable insights for material selection in high voltage systems and applying the AE detection technique to locate the PD events. Industries stand to benefit from material choices, leading to enhanced system reliability and potential cost savings in maintenance.Polymeric materials degrade over time, leading to insulation failures. Finding new materials with strong dielectric properties and robust mechanical strength is crucial for reliable electricity supply. These materials must address defects from manufacturing faults, water tree traces, or mechanical stresses. Polyurethane (PU) is known for its self-healing properties, notably its ability to recover from surface dents due to high elasticity. However, self-healing decreases with increased hardness. This study investigates PU's dielectric breakdown properties at varying hardness levels, revealing an increase in breakdown strength with hardness. Balancing hardness and self-healing are essential, providing insights into PU's dielectric properties. In parallel to engineering novel insulating materials, detecting defects early is crucial to prevent deterioration from partial discharges (PDs). Detecting PDs using acoustic emission (AE) signals is not fully explored for cable insulation. Therefore, the study investigates acoustic pulse propagation from PD events in polymer using finite element methods (FEM) in COMSOL. An analytical model in MATLAB quantifies the impact of multiple propagation paths in a cylinder, aided by a Perfect Matched Layer (PML) in the COMSOL model for reflection-free modelling. The models reveal that acoustic pulse magnitudes decrease rapidly with distance, following the inverse square law. Moreover, the study also explores the effects of PU hardness on the propagation characteristics of the AE signal, revealing a high decay rate in AE signal peak magnitude and energy with increasing PU hardness. Frequency spectra analysis indicates stronger attenuation of higher frequency components with distance. The study's revelations on the impact of PU hardness on AE signal characteristics provide engineers with valuable insights for material selection in high voltage systems and applying the AE detection technique to locate the PD events. Industries stand to benefit from material choices, leading to enhanced system reliability and potential cost savings in maintenance

Електромагнітна сумісність у системах електропостачання

The textbook is devoted to electromagnetic processes connected both with conducted and field electromagnetic interferences. Special attention is paid to interharmonic electromagnetic interference. Questions of electromagnetic compatibility in power networks with wind electric sets, problems of voltage dips and voltage impulses are considered. Active filters are considered as a specific problem of electromagnetic compatibility. Influence of electromagnetic fields on biosphere, of electromagnetic ecology, economic and legal problems of electromagnetic compatibility are presented

Microtechnologies for Discharge-based Sensors.

Microdischarge-based sensors are known to offer advantages such as the ability to operate at temperature extremes and to provide large output signals that do not require local amplification. This work is primarily directed at the design and microfabrication of pressure sensors that use differential microdischarge currents. Two approaches are evaluated. The first uses a common anode and reference cathode located on a glass substrate, whereas a sensing cathode is located on an opposing silicon diaphragm that is deflected by applied pressure. Leads are transferred by electroplated through-glass vias. The second uses a common cathode and reference anode located on a silicon substrate, whereas a sensing anode is located on a thin film diaphragm that deflects under applied pressure. Leads are transferred by through-wafer isolated bulk-silicon lead transfer (TWIST). Fabricated sensors with 200-µm diameter have footprints as small as 300×300 µm2, and volume of ≈0.01 mm3, which is 150× smaller than prior work. The fractional differential current (I1-I2)/(I1+I2) increases monotonically from -0.7 to 0.2 as external pressure increases from 1 atm to 8 atm. The TWIST process can also be used to fabricate ultra-miniature capacitive pressure sensors with backside contacts that minimize the form factor and allow stacking of the sensor on interface electronics. A sensor with a 100-µm diameter diaphragm measures 150×150 µm2 in size. Fabricated sensors with thicknesses of 3 µm (C100t3) and 5 µm (C100t5) have dynamic ranges of 20 MPa and 50 MPa, respectively. Pressure responses in the non-contact mode and the contact mode are 3.1 fF/MPa, 5.3 fF/MPa for C100t3, and 1.6 fF/MPa, 1.6 fF/Ma for C100t5, respectively. This thesis also describes a preliminary exploration of options to initiate microdischarges using scavenged energy – in this case from mechanical impact. A miniature high voltage generator is formed by connecting multiple electrode pairs in series on a single PZT element. This strategy amplifies voltage roughly in proportion to the electrode pair count; a three electrode-pair device is used to successfully initiate microdischarges with peak voltages exceeding 1.35 kV.PhDMechanical EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/111467/1/xinluo_1.pd

Control of Energy Storage

Energy storage can provide numerous beneficial services and cost savings within the electricity grid, especially when facing future challenges like renewable and electric vehicle (EV) integration. Public bodies, private companies and individuals are deploying storage facilities for several purposes, including arbitrage, grid support, renewable generation, and demand-side management. Storage deployment can therefore yield benefits like reduced frequency fluctuation, better asset utilisation and more predictable power profiles. Such uses of energy storage can reduce the cost of energy, reduce the strain on the grid, reduce the environmental impact of energy use, and prepare the network for future challenges. This Special Issue of Energies explore the latest developments in the control of energy storage in support of the wider energy network, and focus on the control of storage rather than the storage technology itself

Water-Tree Modelling and Detection for Underground Cables

In recent years, aging infrastructure has become a major concern for the power industry. Since its inception in early 20th century, the electrical system has been the cornerstone of an industrial society. Stable and uninterrupted delivery of electrical power is now a base necessity for the modern world. As the times march-on, however, the electrical infrastructure ages and there is the inevitable need to renew and replace the existing system. Unfortunately, due to time and financial constraints, many electrical systems today are forced to operate beyond their original design and power utilities must find ways to prolong the lifespan of older equipment. Thus, the concept of preventative maintenance arises. Preventative maintenance allows old equipment to operate longer and at better efficiency, but in order to implement preventative maintenance, the operators must know minute details of the electrical system, especially some of the harder to assess issues such water-tree. Water-tree induced insulation degradation is a problem typically associated with older cable systems. It is a very high impedance phenomenon and it is difficult to detect using traditional methods such as Tan-Delta or Partial Discharge. The proposed dissertation studies water-tree development in underground cables, potential methods to detect water-tree location and water-tree severity estimation. The dissertation begins by developing mathematical models of water-tree using finite element analysis. The method focuses on surface-originated vented tree, the most prominent type of water-tree fault in the field. Using the standard operation parameters of North American electrical systems, the water-tree boundary conditions are defined. By applying finite element analysis technique, the complex water-tree structure is broken down to homogeneous components. The result is a generalized representation of water-tree capacitance at different stages of development. The result from the finite element analysis is used to model water-tree in large system. Both empirical measurements and the mathematical model show that the impedance of early-stage water-tree is extremely large. As the result, traditional detection methods such Tan-Delta or Partial Discharge are not effective due to the excessively high accuracy requirement. A high-frequency pulse detection method is developed instead. The water-tree impedance is capacitive in nature and it can be reduced to manageable level by high-frequency inputs. The method is able to determine the location of early-stage water-tree in long-distance cables using economically feasible equipment. A pattern recognition method is developed to estimate the severity of water-tree using its pulse response from the high-frequency test method. The early-warning system for water-tree appearance is a tool developed to assist the practical implementation of the high-frequency pulse detection method. Although the equipment used by the detection method is economically feasible, it is still a specialized test and not designed for constant monitoring of the system. The test also place heavy stress on the cable and it is most effective when the cable is taken offline. As the result, utilities need a method to estimate the likelihood of water-tree presence before subjecting the cable to the specialized test. The early-warning system takes advantage of naturally occurring high-frequency events in the system and uses a deviation-comparison method to estimate the probability of water-tree presence on the cable. If the likelihood is high, then the utility can use the high-frequency pulse detection method to obtain accurate results. Specific pulse response patterns can be used to calculate the capacitance of water-tree. The calculated result, however, is subjected to margins of error due to limitations from the real system. There are both long-term and short-term methods to improve the accuracy. Computation algorithm improvement allows immediate improvement on accuracy of the capacitance estimation. The probability distribution of the calculation solution showed that improvements in waveform time-step measurement allow fundamental improves to the overall result

Controlled Ecological Life Support Systems (CELSS) conceptual design option study

Results are given of a study to explore options for the development of a Controlled Ecological Life Support System (CELSS) for a future Space Station. In addition, study results will benefit the design of other facilities such as the Life Sciences Research Facility, a ground-based CELSS demonstrator, and will be useful in planning longer range missions such as a lunar base or manned Mars mission. The objectives were to develop weight and cost estimates for one CELSS module selected from a set of preliminary plant growth unit (PGU) design options. Eleven Space Station CELSS module conceptual PGU designs were reviewed, components and subsystems identified and a sensitivity analysis performed. Areas where insufficient data is available were identified and divided into the categories of biological research, engineering research, and technology development. Topics which receive significant attention are lighting systems for the PGU, the use of automation within the CELSS system, and electric power requirements. Other areas examined include plant harvesting and processing, crop mix analysis, air circulation and atmosphere contaminant flow subsystems, thermal control considerations, utility routing including accessibility and maintenance, and nutrient subsystem design

Protection and Disturbance Mitigation of Next Generation Shipboard Power Systems

Today, thanks to modern advances mainly in the power electronics field, megawatt-level electric drives and magnetic levitation are being integrated into the marine power grids. These technologies operate based on Direct Current (DC) power which require Alternating Current (AC) to DC conversion within the current grid. Medium-voltage Direct Current (MVDC) and Flywheel Energy Storage Systems (FESS) are the next state-of-the-art technologies that researchers are leaning on to produce, convert, store, and distribute power with improved power quality, reliability, and flexibility. On the other hand, with the extensive integration of high-frequency power electronic converters, system stability analysis and the true system dynamic behaviors assessment following grid disturbances have become a serious concern for system control designs and protection. This dissertation first explores emerging shipboard power distribution topologies such as MVDC networks and FESS operation with charge and discharge dynamics. Furthermore, the important topic of how these systems perform in dynamic conditions with pulsed power load, faults, arc fault and system protection are studied. Secondly, a communication-based fault detection and isolation system controller that improves upon a directional AC overcurrent relay protection system is proposed offering additional protection discrimination between faults and pulsed-power Load (PPL) in MVDC systems. The controller is designed to segregate between system dynamic short-circuit fault and bus current disturbances due to a PPL. Finally, to validate the effectiveness of the proposed protection controller, different bus current disturbances are simulated within a time-domain electromagnetic transient simulation of a shipboard power system including a PPL system operating with different ramp rate profiles, pulse widths, peak powers, and fault locations. This overarching goal of this work is to address some of the critical issues facing the US Navy as warfighter mission requirements increase exponentially and move towards advanced and sophisticated pulsed power load devices such as high energy weapon systems, high energy sensor and radar systems. The analyses and proposed solutions in this dissertation support current shipbuilding industry priorities to improve shipboard power system reliability and de-risk the integration of new power system technologies for next generation naval vessels